Check if there are any errors in the events for the cluster in question by issuing a kubectl describe cluster cluster-id

Check if all pods for the cluster are running by executing kubectl get pods -n cluster-$CLUSTER_ID

If that is not the case, check the log of the pod in quesiton by issuing a kubectl logs -n cluster-$CLUSTER_ID $PODNAME

If you want to play around with flags or other settings for a pod, you can make Kubermatic stop managing the cluster by running kubectl edit cluster $CLUSTER_ID and setting .spec.pause to true

If you want more detailled logs from Kubermatic, you can edit one of its deployments, e.G. kubectl edit deployment kubermatic-controller-manager-v1 -n kubermatic, and set the verbosity by adjusting the default of -v=2 to e.G. -v=4

Check for problems with machines for an individual user cluster

Get the kubeconfig to your cluster via the UI

Configure kubectl to use it by running export KUBECONFIG=$DOWNLOADED_KUBECONFIG_FILE